For resist compositions used in the microfabrication of semiconductor integrated circuits, one requirement is elimination of resist residues known as scum. The scum is an insolubilized component of resist that arises in the alkali development step following exposure. If scum is left after development, it can cause failures in the subsequent steps such as etching and electrolytic plating, giving rise to the fatal problem that the desirable finished shape cannot be obtained. Since a substantial reduction of line width is in progress in recent years, even the presence of slight scum can create a serious problem. One attempt to alleviate this problem from the developer side is to add specific surfactants to aqueous solutions of commonly used organic bases (such as tetramethylammonium hydroxide) as disclosed in JP-A 6-118660 and JP-A 11-352700.
Improvements have also been made from the resist material side. For resist compositions of the chemical amplification type, JP-A 11-030856, JP-A 11-030865 and JP-A 11-109629 propose the use of specific resins and photoacid generators. These attempts are to improve scum by tailoring the resin or photoacid generator, at the sacrifice of some of the performance factors required for resist materials. Therefore, there is a need for a technique of improving scum while permitting the resin and photoacid generator to be selected from wide ranges.